Electric shot-firing machine



Sept. 13, 1938. K. S-CHAFFLER-GLC3SSL 2,129,835

ELECTRIC SHOT-FIRING MACHINE Filed May '5, 1957 Ratented Sept. 13, 1938UNITED STATES PATENT OFFICE Application May 5, 1937, Serial No. 140,870InAustria April 15, 193':

6 Claims.

This invention relates to electric shot-firing machines equipped withmeans for ensuring the delivery of current of suflicient strength toeffect ignition with certainty.

It is already known to provide handor springdriven shot-firing machineswith an instantaneous contacting device which only closes the currentcircuit through the generator and the shotfiring line at the end of thedriving impulse, that is to say when the armature of the generator hasattained its maximum speed of rotation. In the case of hand-drivenshot-firing machines, however, this maximum speed of rotation dependsupon the manual force and skill used in carrying out the drivingoperation, and it may easily happen, if this operation is performed withinsufiicient energy or skill, that the voltage of the current generatedin the machine is not high enough to ensure faultless firing of all thefuses connected to the machine.

Attempts have been made to overcome this drawback by arranging for thecircuit to be closed by a relay responsive to the voltage of the currentgenerated in the machine. It is impossible, however, with an arrangementof this nature, to preclude with certainty the possibility of the relayeffecting closing of the circuit with some delay, that is to say at amoment of time at which the drop in the voltage of the current generatedby the machine, which occurs immediately after the driving impulseceases, owing to the immediate falling off of the speed of rotation ofthe armature, has already taken effect. Now since with electricshot-firing machines the maximum duration of the firing current may notexceed @30 of a second it will be clear that a very slight error intiming will suflice, under unfavorable circumstances, to render theshort current impulse supplied to the shot-firing line too weak toignite all the fuses connected thereto.

With the shot-firing machine according to the present invention thedanger of the current impulse generated being insuflicient to fire allthe fuses connected thereto, or rather of too weak an impulse beingallowed to flow through the shotfiring line, is avoided with certaintyby the provision of a blocking device for the firing current switchcontact, which only liberates this contact for operation providedthemagnetic field of the firing machine has attained the strengthcorresponding to the requisite voltage of the firing current. If then inthe case of a hand-driven shot-firing machine the voltage of the currentgenerated is not quite high enough, for instance owing to aninsufliciently powerful driving impulse, to ensure faultless firing ofall the fuses the magnetic field in the magnet frame or yoke of themachine does not attain the strength appropriate to the required outputvoltage, and the switch contact consequently remains blocked by themeans provided for this purpose. The shotfiring circuit including thefuses thus remains open, and no current impulse that would be inadequatefor firing all the fuses connected up to the machine can pass into theshot-firing line. The operator of the machine is thus compelled to startagain and to impart a more powerful driving impulse to the machine, andif this be successfully achieved the blocking device is 'put out ofaction, and a current impulse of sufiicient voltage flows into theshot-firing line.

In the accompanying drawing there is shown, diagrammatically, anelectric shot-firing machine according to the invention equipped withmeans for blocking and releasing the switch contact in dependence on thestrength of the magnetic field of the current generator. In theshotfiring machine, which consists in a known manner of the armature i,magnet core 3, magnet field coil 2, and toothed sector 4 adapted to bedriven by means of a handle in the direction indicated by the arrow andto effect rotation of the armature through the instrumentality ofintermediate gearing not shown in the drawing, the switch contact forthe firing current, which may consist for instance of the switch pin 5,the slide 6, and the leaf springs I, is operated by means of the pawl 8mounted on the toothed sector 4. This pawl bears slidingly against theend of the slide 6 during the movement of the sector amounting to aboutone-third of a complete revolution, thereby moving this slide andcausing the switch pin 5 to pass between the springs l, with the resultthat the current circuit through the machine and the fuses 9 ,is closed.After the pawl 8 comes clear of the slide 6 this latter and the pin 5are restored to the circuit-breaking position by the previouslycompressed spring Ill. The length of time elapsing betweencircuitclosing and circuit-interruption amounts at the most to 7 sec.

In order to ensure that the contacting device 5, '6 shall not be able toeffect circuit closing when the speed of rotation of the armature l isless than is necessary to generate a current of suflicient voltage theslide 6 is blocked by means of a latch II the end of which engages in anotch l5 in the slide. The blocking thus effected is only cancelled whenthe magnetic field of the machine, after having increased in strengthuntil the voltage of the current generated in the machine has attained apredetermined figure, attracts an armature l3 mounted on the blockinglatch l I, through the intermediary of a pole piece I! connected withthe magnet core 3 and magnetized thereby. Provided the switch contact beliberated immediately before the moment at which the current impulsegenerated by the armature reaches its maximum value, the circuitclosingwill be effected when the voltage is at its maximum. Ii. however, inconsequence of too weak a driving impulse being imparted to the Sector 4in operating the machine, only a current of somewhat too low a voltageis generated, the magnetic field set up will be correspondingly tooweak, with the result that the armature l3 on the latch II is notattracted and the current circuit remains open. A current impulse thatis not sufficient to ensure ignition of all the fuses connected up tothe machine can not, therefore, pass into the shot-firing line.

After interruption of the current and disappearance of the efiectivemagnet field between the parts l2 and IS, the latch H returns into itslocking position under the influence of its spring H.

I claim:

1. In a dynamo-electric shot-firing machine the combination with anigniting circuit including a charge igniting device, of an electriccurrent generator in said igniting circuit, spaced contacts in saidcircuit, means for momentarily bridging said contacts and therebyclosing said circuit, means for operating said generator havingassociated therewith means for imparting an operating impulse ofpredetermined extremely short duration to said circuit-closing means, adetaining contrivance normally arrestingly engaging in said impellingmeans and operatively responsive to the strength of the magnetic fieldof said generator to release said impelling means only when the strengthof said magnetic field reaches a predetermined value. 2. In adynamo-electric shot-firing machine the combination with an ignitingcircuit including a charge igniting device, of an electric currentgenerator having a field magnet yoke and disposed in said ignitingcircuit, spaced contacts in said circuit, means including a slidingthrust member for momentarily bridging said contacts 'and therebyclosing said circuit, means for operating said generator havingassociated therewith means for imparting an operating impulse ofpredetermined and extremely short duration to said circuit-closingmeans, -a movable latch normally arrestingly engaging in said thrustmember, and a magnet armature mounted on said latch within the range ofthe lines of force proceeding from the said magnet yoke, said latch andarmature being so disposed that said latch is moved out of engagementwith said thrust member when the strength of the magnetic field of saidgenerator reaches a predetermined value.

3. In a dynamo-electric shot-firing machine the combination with anigniting circuit including a charge igniting device, of an electriccurrent generator having a field magnet yoke and disposed in saidigniting circuit, a pole piece made of magnetizable material andconductively connected with the said magnet yoke, spaced contacts insaid circuit, means including a sliding thrust member for momentarilybridging said contacts and thereby closing said circuit, means foroperating said generator having associated therewith means for impartingan operative impulse of predetermined and extremely short duration tosaid circuit-closing means, a movable latch normally arrestinglyengaging in said thrust member, and a magnet armature mounted on saidlatch for attraction to said pole piece to move said latch out ofengagement with said thrust member when the strength of the magneticfield of said generator reaches a predetermined value.

4. In a dynamo-electric shot-firing machine the combination with anigniting circuit including a charge igniting device, of an electriccurrent generator having a field magnet yoke and disposed in saidigniting circuit, a pole piece made of magnetizable material andconductively connected with the said magnet yoke, spaced contacts insaid circuit, means including a sliding thrust member for momentarilybridging said contacts and thereby closing said circuit, said thrustmember having an abutment surface accessible from the direction towardswhich said member is adapted to move in the circuit-closing operation,means for operating said generator having associated therewith means forimparting an operative impulse of predetermined and extremely shortduration to said circuit closing means, a movable latch normallyengaging against said abutment surface to detain said thrust member, anda magnet armature mounted on said latch for attraction to said polepiece to move said latch out of engagement with said abutment surfaceand thereby to liberate said thrust member for operation in response tosaid impelling means when the strength of the magnetic field of saidgenerator reaches a predetermined value.

5. In a dynamo-electric shot-firing machine the combination with anigniting circuit including a charge igniting device, of an electriccurrent generator having a field magnet yoke and disposed in saidigniting circuit, a pole piece made of magnetizable material andconductively connected with the said magnet yoke, spaced contacts insaid circuit, means including a sliding thrust member for momentarilybridging said contacts and thereby closing said circuit, said thrustmember having a recess presenting an abutment surface accessible fromthe direction towards which said member is adapted to move in thecircuit-closing operation, means for operating said generator havingassociated therewith means for imparting an operative impulse ofpredetermined and extremely short duration to said circuit-closingmeans, a movable latch normally engaging against said abutment surfaceto detain said thrust member, and a magnet armature mounted on saidlatch for attraction to said pole piece to move said latch out ofengagement with said abutment surface and thereby to release said thrustmember for operation in response to said impelling means when thestrength of the magnetic field of said generator reaches a predetermined value.

6. In a dynamo-electric shot-firing machine the combination with anigniting circuit including a charge igniting device, of an electriccurrent generator having a field magnet yoke and disposed in saidigniting circuit, a pole piece made of magnetizable material andconductively connected with the said magnet yoke, spaced contactsinterposed in said circuit, means including a sliding thrust member formomentarily bridging said contacts and thereby closing said circuit,said thrust member having a recess presenting an abutment surfaceaccessible from the direction towards which the said thrust member isadapted to move in the circuit-closing operation, means for operatingsaid generator having associated therewith means for imparting anoperative impulse of predetermined and extremely short duration to saidcircuit closing means, a movable latch spring stressed into engagementagainst said abutment surface to detain said thrust member, and a magnetarmature mounted on said latch for attraction to said pole piece to movesaid latch clear of said abutment surface against the action 10 of saidspring and thereby to release said thrust member for operation inresponse to said impelling means when the strength of the magnetic fieldof said generator overcomes the strength of said spring, said springbeing also adapted to restore said latch to its initial position inengagement in front of said abutment surface after discontinuance of themagnetic field in said yoke and pole piece and after the said thrustmember has returned into its inoperative position.

KONRAD SCHAFFLER-GLCSSL.

